World Overrun by Zombies, but I have Transmigration Perks!

“A country once killed those it had summoned, cause summoning rituals to fail thereafter. Therefore, I shall spare your life. You should be grateful for the noble sacrifices of your predecessors.”

Three years ago, Hayato Kumakura was summoned to another world. After defeating the Demon Lord, he was sent back to Earth.

However, upon his return, Earth had been plagued by a zombie outbreak that started three years earlier. Armed with the powers of a summoned one, Hayato dominates in a world overrun by zombies.